Bone is made up of a hard outer core, known as cortical bone or cortical plate, and a soft spongy interior known as cancellous bone or trabecular bone, which includes a marrow filling in the porous space within the spongy bone (commonly referred to as bone marrow). The cortical plate is very hard and provides the rigid structure to the skeleton, which allows the skeleton to bear weight. Bone marrow is rich in capillary beds.
A traditional bone marrow aspiration needle is commonly used to access marrow from the hip or iliac bone. The traditional aspiration needle includes an aspiration cannula (also referred to as a cannulated trocar) and a removable stylet that extends through the cannula and has a sharp pointed tip. Because the traditional aspiration needle is stiff, the needle can only advance linearly within the marrow space. Once the needle is through the cortical plate, the cannula only has access to whatever marrow is directly ahead of the cannula tip, but cannot bend or access marrow to the sides of the cannula. Thus, clinicians often need to perform multiple punctures in order to gain larger volumes of aspirate from a more diverse cross section of the marrow space. Since the hip bone is long and thin, once the traditional aspiration needle has penetrated cortical bone, the sharp and stiff instrument has the potential to penetrate through the other side of the cortical bone, resulting in significant trauma. Consequently, it is important for the surgeon to have a proper angle and skilled technique to ensure a safe aspiration. Since the iliac crest curves from the front to the back of the patient, the best angle of entry is from the back. Since the stylet is made of a stiff material, once inside the spongy bone, the needle assembly can only go straight, thus requiring multiple punctures to obtain the required volume of aspirate.
A traditional marrow aspiration needle is meant to access bone marrow from larger cavities and is not ideally suited to drawing marrow from the smaller confines such as the vertebral body of the spine. Because of the sharpness and stiffness of a traditional aspiration needle, using such an instrument in the small curved marrow space of a vertebral body would greatly increase the likelihood of introducing trauma. Less invasive and safer methods to access the marrow tissue of the vertebral body are needed in an effort to support the emerging field of orthobiologics. One fast growing area of this field combines marrow aspirate with synthetic matrix material in order to facilitate instrumented assisted spinal fusion.